Reframing loss of efficacy in sacral neuromodulation: a neurofunctional service model for coloproctology

Sacral neuromodulation (SNM) is an established therapeutic option for fecal incontinence, low anterior resection syndrome (LARS), and selected bowel dysfunction phenotypes encountered in colorectal practice. Despite durable benefit in many patients, secondary loss of efficacy (LOE) remains a common long-term management problem and is often interpreted primarily through a mechanical lens.

To refine a conceptual neurofunctional service model for LOE in SNM and to translate it into a more clinically applicable framework for coloproctological practice.

For the purposes of this paper, LOE is defined as deterioration after a previously effective phase, operationalized by one or more of the following: loss of at least 50% of the initial clinically meaningful benefit; deterioration of five or more points on a validated symptom instrument (Wexner Continence Score, LARS Score, or equivalent), or documented worsening in a structured patient symptom diary; or sustained patient-reported decline over at least two consecutive assessments, after exclusion of technical failure. We propose a structured pathway comprising confirmation of LOE, systematic technical exclusion, minimum neurofunctional reassessment, phenotype-guided reprogramming, predefined reassessment intervals, and explicit thresholds for revision or explantation. Terms such as neuroadaptive drift and phenotype mismatch are presented as explanatory hypotheses rather than established mechanisms.

Viewing SNM as a dynamic network-modulating therapy rather than a static device intervention may reduce unnecessary procedural escalation and improve the consistency of long-term management. The proposed model is intended as an implementable service framework for structured follow-up and reprogramming in patients with suspected LOE.